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ARS Home » Northeast Area » Orono, Maine » New England Plant, Soil and Water Research Laboratory » Research » Publications at this Location » Publication #175233
Title: OCCURRENCE AND CROSS-INFECTION OF PHYTOPHTHORA INFESTANS ON HAIRY NIGHTSHADE (SOLANUM SARRACHOIDES) AND POTATO (SOLANUM TUBEROSUM) IN MAINE

Author
item Olanya, Modesto
item LAMBERT, D - UNIVERSITY OF MAINE
item PLANT, A - UNIVERSITY OF MAINE

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Research Notes
Publication Acceptance Date: 5/2/2005
Publication Date: 9/1/2005
Citation: Olanya, O.M., Lambert, D.H., Plant, A.B. 2005. Occurrence and cross-infection of phytophthora infestans on hairy nightshade (solanum sarrachoides) and potato (solanum tuberosum) in maine. Canadian Journal of Plant Pathology. v 27: p458-460.

Interpretive Summary: Late blight, caused by Phytophthora infestans, is a significant potato disease in all potato growing regions of the world. Identification of additional hosts is critical for understanding potential sources of inoculum. In 2004, late blight was observed on leaves and stems of hairy nightshade (Solanum sarrachoides Sendt,) a common weed in many potato fields in Maine. Diseased nightshade plants were detected in two of eighteen locations having potato late blight. Lesions from diseased nightshade leaves ranged from 0.25 to 9 cm2 and on diseased stems ranged from 4.5 to 13.8 cm. Isolations of diseased samples, and microscopic observations confirmed the presence of P.infestans. Based on allozyme analysis, representative isolates of P. infestans from hairy nightshade were identified as the US 8 genotype. Diseased leaves from nightshade were shown to cause disease on potato leaves and tubers. Similarly, P. infestans from potato caused disease on nightshade. These results suggest that hairy nightshade may be involved in the perpetuation of late blight in potato. Management practices for controlling hairy nightshade should be followed for potato production.

Technical Abstract: Late blight, caused by Phytophthora infestans, is a significant potato disease in all potato growing regions of the world. Identification of additional hosts is critical for understanding potential sources of inoculum. In 2004, late blight was observed on leaves and stems of hairy nightshade (Solanum sarrachoides Sendt), a common weed in many potato fields in Maine. Diseased nightshade plants were detected in two of eighteen locations having potato late blight. Lesions from diseased nightshade leaves ranged from 0.25 to 9 cm2 and on diseased stems ranged from 4.5 to 13.8 cm. Isolations of diseased samples, and microscopic observations confirmed the presence of P.infestans. Based on allozyme analysis, representative isolates of P. infestans from hairy nightshade were identified as the US 8 genotype. Cross-infection of nightshade and potato leaves (Shepody), as well as potato tubers (Yukon Gold) was obtained with both hairy nightshade and potato inoculum sources. The frequency of infection of hairy nightshade and potato at 18 C was 50 and 67% respectively, when the inoculum source was hairy nightshade, and 73 and 83% when the inoculum source was potato. This is the first report to demonstrate that hairy nightshade can serve as an alternate host and inoculum source of P. infestans to potato in Maine. Management practices to control hairy nightshade should be followed for potato production.